Recently, a head-mounted display has been provided for practical use as a device that enlarges a two-dimensional image by using a virtual image optical system and displays the enlarged virtual image to allow an observer to observe the enlarged virtual image.
The head-mounted displays are classified into a see-through transmissive head-mounted display and a non-transmissive head-mounted display. Because the transmissive head-mounted display is used in combination with an information terminal or used to provide augmented reality (AR), the transmissive head-mounted display needs to have a small size and excellent portability. In addition, because the non-transmissive head-mounted display is used to watch movies, or provide games, virtual reality (VR), or the like, the non-transmissive head-mounted display needs to have a wide viewing angle in which a sense of immersion is obtained.
The head-mounted display is disclosed in, for example, Patent Document 1. The head-mounted display disclosed in Patent Document 1 is provided with a display device which displays an image, a light guide member to which the image displayed on a display element is inputted, and a propagation means which totally reflects the inputted image in the light guide member to propagate the inputted image toward a user's pupils. Further, the light guide member is made of a glass material having a refractive index of about 1.7 in order to obtain a predetermined viewing angle.